The invention relates to a component for holding down measuring leads and measuring devices in a groove, provided therefor, of a machine part.
It is known to monitor machines, such as thermal turbomachines for example, during operation by means of special measuring devices in order to be able to quickly detect faults in the machine. On the one hand, it is thus possible, on account of manual or automatic corrections immediately carried out, to prevent damage to the machine in the operating state or, in the worst case, stoppage of the machine; on the other hand, such measurements provide for potential improvements to the machine by weak points being detected.
The measuring leads are laid in grooves which are normally milled in the relevant machine parts. In order to ensure that the measuring leads remain in the grooves provided for them when they are fitted, special componentsxe2x80x94xe2x80x9chold-downsxe2x80x9dxe2x80x94have to be used.
For example, it is known to use a heavy-duty spring dowel sleeve as a hold-down for measuring leads which are used in gas turbines. In this case, the heavy-duty spring dowel sleeve is pressed into a transverse groove which is arranged perpendicularly to the groove for the measuring leads. Disadvantages with this solution are, on the one hand, the high costs which are caused by the requisite very exact flanks when milling the transverse groove and, on the other hand, inevitable breakdowns on account of the point-like contact, which can scarcely be avoided, of the heavy-duty spring dowel sleeve on the measuring lines or measuring devices.
It has been attempted to avoid these disadvantages by means of another known technical solution in which spaced-apart holes are made along the groove, arranged in the machine part, for accommodating the measuring leads. These holes have a diameter which is larger than the groove width. The depth of the holes is less than the depth of the groove. In order to hold down the measuring leads in the groove, snap rings which are open on one side are inserted into the holes. However, these snap rings require an undercut groove for fitting and clamping, so that the cost of production is also relatively high with this solution. A further disadvantage consists in the fact that the snap ring only has a small clamping force, which even decreases during operation of the gas turbine, so that the snap ring jumps away in a spring-loaded manner and can thus no longer perform its task as a hold-down.
The invention attempts to avoid these disadvantages of the known prior art. The object of the invention is to develop a component for holding down measuring leads and measuring devices in a groove, provided therefor, of a machine, which component, on the one hand, can be produced in a simple and thus cost-effective manner and, on the other hand, can be fitted easily and without special tools, and also reliably holds the measuring leads in the groove during widely varying operating conditions of the machine.
This object is achieved according to the invention in that the component is designed in the form of a disk which has a cutting edge on its circumference, the cutting edge not being formed continuously but consisting of two partial cutting edges circumferentially opposite one another. An opening in the form of a hexagon socket is arranged centrally in the disk.
The method of fitting the disk according to the invention is characterized in that first the disk is put into the hole of the groove in such a way that the two partial cutting edges point in the longitudinal direction of the groove, in that a hexagon socket key is then inserted into the opening of the disk, and in that finally the key is turned while the disk is pressed down at the same time, so that the cutting edges cut into the material of the machine part and jam tight.
The advantages of the invention consist firstly in the fact that the component according to the invention can be produced in a cost-effective manner, for it is a component of very simple design. Secondly, it is advantageous that no special tools are required for fitting the component into the groove. The hole to be made in the groove of the machine component for accommodating the component according to the invention is a perfectly normal hole without a specially required tolerance or without an undercut groove. This technical solution also provides for simple standardization. New disks fit without any problems into old holes and old disks into new holes.
It is expedient if the cutting edge is arranged at half the height of the disk and has a flank angle xcex1/2 of 30xc2x0. In this case, no canting occurs during the fitting.
Furthermore, it is advantageous if the disk for holding down the measuring leads in the groove of the machine part is made of an austenitic steel and the machine part with the groove is in contrast made of a ferritic material. Since the austenitic material has a higher coefficient of thermal expansion than the ferritic material, the austenitic disk, during operation, expands more than the ferritic machine part with the groove on account of the generation of heat. Consequently, the disk jams, so that it sits very tightly in the groove and ensures robust holding-down of the measuring leads.